1. Field of the Invention:
The present invention generally relates to a device and a method for controlling a liquid crystal display and, more particularly, to a controlling circuit and a controlling method for overdriving a video signal in a liquid crystal display so as to eliminate image blur and improve the display quality.
2. Description of the Prior Art:
The user communicates with an electronic device through messages processed by the display of the electronic device so as to make the most of the electronic device. The computer is an example of such an electronic device.
The liquid crystal display (LCD) is the most popular display due to its small size and lightness. The LCD pixels are arranged in an array and each of the pixels is provided with electrodes so that a voltage is applied to the liquid crystal molecules for controlling the alignment of the liquid crystal molecules that determines the transmissivity of light passing the liquid crystal molecules. Accordingly, a video can be displayed by way of controlling the alignment of liquid crystal molecules.
Please refer to FIG. 1, which is a timing diagram showing the relation between the pixel voltage and the transmissivity of light, where the solid line represents the pixel voltage and the dotted line L represents the transmissivity of light. Due to the slow response time of the liquid crystal molecules, when the pixel voltage in a liquid crystal display is switched from V1 to V2, the liquid crystal molecules can not turn to a pre-determined direction for achieving a pre-determined transmissivity of light within a frame time (T), resulting in image blur.
In order to overcome image blur, a method for overdriving liquid crystal molecules is used in a liquid crystal display. Please refer to FIG. 2, which is a timing diagram showing the relation between the pixel voltage and the transmissivity of light when a conventional method for overdriving liquid crystal molecules is used. When the pixel voltage in a liquid crystal display is switched from V1 to V2, the liquid crystal molecules are accelerated by applying a higher voltage V3 to turn to a pre-determined direction so as to achieve a pre-determined transmissivity of light within a frame time (T). The response time of a liquid crystal display replies on the twisting speed of liquid crystal molecules. The faster the twisting speed, the shorter the response time.
However, the aforesaid technology still has some drawbacks. For example, when the frame is switched from a low luminance value to a high luminance value (much higher than the low luminance value), noise associated with the great amount of signals overdriven increases as the frame signals are overdriven. This leads to degraded video quality, which requires to be improved.
Therefore, there is need in providing a device and a method for controlling a liquid crystal display so as to improve the conventional technology for overdriving the video signal.